Ian Batten wrote:
> Clearly a day which consists of 86400 SI seconds isn't a mean solar day over
> any extended period of time.
Indeed.
> One of "86400" or "SI" or "a day runs from mean noon to mean noon" has to go
> at some point many thousands of years out.
A good place to start, although there is also a family of solutions that handle
the daily epsilon corrections explicitly. Sort of like compounding interest.
These include, from Mark Calabretta:
http://www.ucolick.org/~sla/navyls/0459.html
(Who was also quite eloquent that a leap second is purely a representational
overlay of TAI.) And Steve Allen's TZ database concept:
http://www.cacr.caltech.edu/futureofutc/preprints/45_AAS_11-681_Allen.pdf
Several of us find the notion of attempting to redefine the word "day"
singularly unconvincing:
http://arxiv.org/abs/1106.3141
There has been widespread agreement that lengthening the scheduling horizon for
leapseconds would help, e.g., see the final slide of:
http://phk.freebsd.dk/pubs/usno_slides.pdf
Or the "Extended Prediction" paragraph on p.9 of:
http://www.cacr.caltech.edu/futureofutc/preprints/01_AAS_11-660.pdf
As well as various messages here.
> Does my watch, set to widely available timescales, allow me to catch trains
> on time? That's pretty much the beginning and end of civil time. Literally,
> as that's pretty much how civil time arose in the first place.
And yet many arguments here have proceeded from the observation that civilians
rely on complex modern infrastructure. For instance, a lot of
telecommunications depends on satellite technology, hence the sponsorship of
the Future of UTC meeting by the American Astronautical Society and the
American Institute of Aeronautics and Astronautics. Modern technology depends
on both kinds of timekeeping. A conceptual model recognizing the distinction
is necessary.
Rob
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